The present invention relates to the field of optical beam steering and, more particularly, to a scanning apparatus and associated method using vertical-cavity surface-emitting lasers (VCSELs) and a movable lens to provide a steerable agile beam.
Detecting, tracking, and/or communicating with an object moving within a spatial field, also known as a field of search, has many practical and strategic military and commercial applications. Interaction with such a moving object typically involves directing a single detection beam in a raster pattern so as to scan the beam over the field of search. That is, the detection beam is usually guided in a continuous serial pattern such that it is scanned over the search field to cover the entire area thereof If a portion of the detection beam is reflected, an object will likely have been detected by the detection beam during a scan of the search field. However, additional data relating to the object, such as speed and trajectory, may not be determinable until the detection beam has completed the raster scan and returned to the location of the object in the search field. As such, in certain applications, such as military applications, where moving objects may be traveling at a rate of several times the speed of sound, a raster scan detection system may be too slow to be of practical use with modern systems which are continuously increasing in processing speed. Thus, there exists a need for a system capable of scanning, detecting, and/or communicating with a moving object in a faster, more accurate, and more efficient manner than a raster system.
In addition, a raster system typically requires complex mechanisms and controls for moving the detection beam in the desired raster pattern. For example, where the search field is a square box, the raster pattern may comprise lateral movement of the beam in an alternating manner across the width of the box, with a longitudinal shift equal to the width of the beam with each lateral reversal of the direction of the beam. Such a scan may start at one corner of the box and end at the opposite diagonal corner, where the beam then reverts back to the initial comer to begin the next scan of the search field. Accordingly, the associated mechanisms and controls may be complex and are usually required to be both accurate and durable in order to maintain precise and optimum operation of the detection system. Thus, there exists a further need for a system capable of scanning, detecting, and/or communicating with a moving object that has a simpler operational mechanism, compared to a raster system, with sufficient accuracy and durability to provide a precise detection system.
In certain applications, such scanning, detection, and/or communications systems may be subject to a harsh environment, wherein the system may be exposed to, for example, severe vibrations, g-forces, jarring, and/or impact. Such environmental factors may be detrimental to the performance of a raster-type system. Thus, there exists a further need for a system capable of scanning, detecting, and/or communicating with a moving object that has a simpler and more robust configuration, compared to a raster system, so as to provide a precise and reliable detection system, even in harsh environments.
An example of such a scanning, detection, and/or communication system is disclosed by U.S. Pat. No. 5,909,296 to Tsacoyeanes. The ""296 patent discloses wide angle beam steering using spherical laser diode arrays. A curved array of lasers causes discrete narrow infrared light beams to be projected within a wide field of view, without requiring mechanical motion of components. However, the Tsacoyeanes device may be difficult to produce due to the precise hemispherical configuration in which the lasers must be placed in order to provide the desired accuracy. In addition, the hemispherical configuration may produce a device having undesirable minimum size constraints as well as a disadvantageous maximum laser density constraint. Further, as disclosed, the Tsacoyeanes device relies upon alignment of individual laser beams with the target in order for the device to function as intended. A gap may therefore exist between adjacent laser elements such that less-than-optimum resolution may be obtained as the device shifts from one laser element to the next. Thus, where an array-type device is used, there exists a need for the system to be capable of transitioning between adjacent laser devices in a xe2x80x9cseamlessxe2x80x9d manner and without a significant loss of resolution.
Thus, there exists a need for a detection/communication system capable of scanning, detecting, and/or communicating with a moving object in a faster, more accurate, and more efficient manner than a raster system. Such a system should also have a simpler operational mechanism with sufficient accuracy and durability to provide a precise detection system and a more robust configuration such that the detection system is reliable, even in harsh environments. In instances where such a system is accomplished by use of an array-type device, the system should be capable of transitioning between adjacent laser devices in a xe2x80x9cseamlessxe2x80x9d manner without a significant loss of resolution.
The above and other needs are met by the present invention which, in one embodiment, provides a scanning apparatus for tracking a remote object that is typically moving within a predetermined distance range. A plurality of individually actuatable laser devices are provided, typically in the form of an array, for emitting laser beams. A moveable lens member is disposed proximate to the laser devices such that the laser beams are directed therethrough. The lens member is moveable and cooperable with the laser devices such that each laser beam is directed in a different direction after passing through the lens member. The apparatus is therefore configured to provide laser beam agility by selectively actuating the laser devices and to provide laser beams steerability by moving the lens member with respect to the laser devices.
According to one advantageous embodiment of the present invention, the laser devices comprise vertical-cavity surface-emitting lasers (VCSELs), wherein, in some instances, the VCSELs are solder-bumped to a substrate so as to form a fine pitch, solder-bumped VCSEL array. According to some embodiments, the laser devices may be arranged in a substantially planar array. In other instances, a plurality of sub-arrays of VCSELs may be combined to form the array.
The lens member is disposed in spaced parallel relation to the array and is moveable within a plane corresponding thereto. The lens member may be moved by at least one actuator in communication therewith, such as a piezoelectric actuator. In this configuration, the laser devices are also individually and selectively actuatable such that sequential actuation of individual laser devices coarsely attunes the laser beams to a corresponding trajectory of the moving object to enable the apparatus to track the moving object. Movement of the lens member with respect to an actuated laser device thereafter finely attunes the corresponding laser beam to the trajectory. As such, the scanning apparatus of the present invention can reliably track moving objects in a rapid manner without using a single laser device to raster scan through the entire area of interest.
According to advantageous embodiments, the lens member is configured to cooperate with the laser beams to provide a predetermined magnitude of angular coverage depending on the desired configuration and capabilities of the apparatus. Accordingly, the apparatus is capable of tracking moving objects within a distance range of between about 500 meters and about 2500 meters. In some instances, the apparatus may further comprise a controller capable of individually and selectively actuating the laser devices, wherein sequential actuation of individual laser devices by the controller coarsely attunes the respective laser beams to a corresponding trajectory such that the apparatus is capable of tracking a moving object. The controller may also be configured to direct movement of the lens member with respect to the laser devices so as to finely attune the laser beams to the trajectory. The apparatus may further comprise a detection device for detecting signals from the remote object. In some instances, the controller may be responsive to the detection device so as to actuate the laser devices and move the lens member in order to track the remote object.
Another advantageous aspect of the present invention comprises a method of tracking remote objects. First, an array of laser devices capable of emitting laser beams therefrom is provided in spaced relation to a moveable lens member to form a scanning apparatus configured such that the laser beams are directed through the lens member. The lens member is configured so as to direct each laser beam in a different direction. Selected laser devices are thereafter sequentially actuated such that the emitted laser beams directed through the lens member are coarsely attuned to a trajectory of a remote object. The lens member may also be selectively moved with respect to an actuated laser device such that the laser beam emitted thereby is finely attuned to the trajectory of the remote object.
In some instances, a solder-bumped array of vertical-cavity surface-emitting lasers (VCSELs) is provided in spaced relation to the moveable lens member. In further instances, the method may include interacting with the remote object by transmitting signals to the remote object and receiving signals from the remote object, wherein the received signals may comprise reflections of the laser beams. In response to the signals received from the remote object, a selected laser device may be actuated and/or the lens member moved so as to facilitate communication with the remote object.
Thus, a scanning apparatus and method according to embodiments of the present invention provides a detection/communication system and method capable of scanning, detecting, and/or communicating with a remote object in a faster, more accurate, and more efficient manner than a raster system since the plurality of laser devices allows a multiplexed approach to examining the area of interest. Embodiments of a scanning apparatus according to the present invention also provide a simpler operational mechanism, as a result of selective actuation of individual laser devices having at least a reduced amount of moving parts compared to a raster system, with increased accuracy and lower scanning and detection times, while being durable and robust so as to provide a precise detection system that is reliable, even in a harsh environment. Both the coarse and fine attunement provisions provide more accurate tracking and allow for transitions between adjacent laser devices in a relatively seamless manner, without a significant loss of resolution. Therefore, embodiments of a scanning apparatus and method according to the present invention provide advantages over conventional detection/communication systems.